Carbon quantum dots acting as a new class of “zero-dimensional” carbon nanomaterials have attracted much attention. Hydrothermal carbonization method has been by far one of the most widely used synthesis methods. Many kinds of raw materials can be selected for preparing carbon quantum dots via hydrothermal carbonization method. The preparation process of hydrothermal carbonization is simple. It is able to obtain the carbon quantum dots with abundant oxygen-containing functional groups on the surface and showing excellent water solubility via hydrothermal carbonization. Furthermore, surface functional modification of carbon quantum dots can be carried out during the preparation process. The carbon cores of hydrothermal carbon quantum dots are graphite or amorphous structures. The structures and properties of hydrothermal carbon quantum dots are influenced mainly by raw material types and preparation conditions (including hydrothermal carbonization temperature, time and chemical additives). The products have found good applications in the fields of photocatalysis technology, analysis and detection, the vivo imaging and cellular labeling, light-emitting diodes (LED), drug delivery and so on. In this review, the preparation, properties, formation mechanism (including dehydration, polymerization, carbonization and passivation progress of raw materials) and luminescence mechanism (including surface defect state effect and quantum size effect) of hydrothermal carbon quantum dots are summerized. Simultaneously, the applications of hydrothermal carbon quantum dots are reviewed. The problems remaining to be solved are summarized and the future developments are prospected.
Contents
1 Introduction
2 Preparation of hydrothermal carbon quantum dots
2.1 Influence of feedstocks
2.2 Influence of preparation conditions
3 Properties of hydrothermal carbon quantum dots
3.1 Surface chemical structure
3.2 Crystal structure
3.3 Optical property
4 Formation mechanism of hydrothermal carbon quantum dots
5 Luminescence mechanism of hydrothermal carbon quantum dots
5.1 Surface defect state effect
5.2 Quantum size effect
6 Applications of hydrothermal carbon quantum dots
6.1 Photocatalysis
6.2 Detection probes
6.3 Bioimaging
6.4 Drug delivery
6.5 Light-emitting diodes
6.6 Other applications
7 Conclusion